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r r PROBLEM ASSESSMENT REPORT AND CORRECTIVE CORRECTIVE ACTION PLAN FOR CANEPA'S CAR WASH STOCKTON, CALIFORNIA r 1.0 INTRODUCTION ' Condor Earth Technologies, Inc. (Condor) prepared this Problem Assessment Report(PAR) at the request of Mr. Remo Canepa, property owner, to summarize the investigation of the release of petroleum hydrocarbons to soil and groundwater at Canepa's Car Wash, 6230 Pacific Avenue, Stockton, California (Figure 1). The business consists of an automated car washing facility, a fuel station, and a convenience store. Gasoline and diesel fuel were released from underground storage tanks, piping, and spills on the site. A summary of the environmental sampling and analyses of soil and groundwater samples associated ' with investigation of the site of the former underground storage tanks (USTs) is presented in this report. This report also contains a Corrective Action Plan (CAP) for limited additional assessment of the extent of soil and groundwater degradation, a feasibility study of the actions proposed for clean up, and proposed clean-up levels for the degraded soil and groundwater. Initial investigation of the site including tank removal and soil over-excavation was carried out by WHF Environmental (WHF) in 1993. Condor began site investigation in 1996. A description of the site is presented in Section 2.0 of this PAR, and a historical background of investigation of the site is presented in Section 3.0. The hydrogeology of the site is described in Section 4.0, and the distribution of contamination in soil and groundwater is presented in Section 5.0. A summary of the Sensitive Receptor ' Survey and a Tier I Risk-Based Corrective Action Evaluation are presented in Section 6.0. The alternatives for corrective action and feasibility analyses of those alternatives are presented in Section 7.0. Target Clean-up levels are presented in Section $.0. 2.0 SITE DESCRIPTION Canepa's Car Wash is located in a heavily urbanized area of Stockton. The business consists of an ' automated car wash, a gasoline/diesel fuel station, and a convenience store. The business area is paved with either concrete or asphalt. A plan of the facility is presented in Figure 2. Also located on the plan are the monitor wells, soil vapor extraction wells, and soil borings installed during the investigations and remedial actions carried out to date. 3.0 HISTORICAL BACKGROUND Between February 25, and March 3, 1993, inree undue-grutiiiu storage tailna (USTS' Vu 1 Lucca, aiiu ui��.x,o.,5 were removed by WHF Environmental (WIT) and replaced with a doubled walled system. The removed USTs consisted of two 12,000-gallon gasoline USTs and one 5,000-gallon diesel UST. Approximately 600 icubic yards of contaminated soil were removed from the UST excavation area. The excavated soil subsequently was characterized and disposed of at Forward Landfill in Manteca, California. At least 16 soil samples were collected from the tank excavation for laboratory analyses. The laboratory results indicated predominantly low TPH-G (gasoline at <15 mg/kg) and low BTEX concentrations. One (1) soil sample • collected from the northeastern sidewall of the tank excavation contained 773 mg/kg TPH-G and BTEX M CONDOR